The present invention relates generally to an apparatus for continuously cleaning solvent from waste air and, in particular, to an apparatus for the regeneration of the solvent receiving medium and for the recuperation of the solvent.
A process and a device for the continuous cleaning of solvent containing waste air, for example industrial waste air, with the simultaneous recuperation of the solvent media, is described in the Swiss patent application No. 04 500/87-6 by the inventor of the present invention. In this process and in this device, a commercially available adsorption medium is utilized in two adsorption towers connected in series by pipes, which medium preferentially adsorbs water due to its high polarity. Eventually, already adsorbed substances of low polarity, such as for instance solvents, are displaced by the water. By this adsorption process, the industrial waste air is directed through the medium in one direction, the contaminates removed from the waste air and the purified waste air exhausted to the environment.
In order to obtain a definite separation between the accumulated water and the contaminates, a humidity sensor is positioned at the end of the flow path through the first adsorption tower. As soon as the first adsorption tower is saturated with water, the humidity sensor responds by stopping the flow of air through the first tower and switching on an identical parallel second device for a continuous cleaning operation. Simultaneously with the saturation of the first adsorption tower, all displaced noxious materials of low polarity are accumulated in the second adsorption tower. By an appropriate switching-over, dry warm air is directed in the opposite direction through the first adsorption tower, which air picks up the water deposited in the adsorption medium and is exhausted as humid heated air to the environment. The solvents deposited in the second adsorption tower are desorbed or evaporated by a counter flow current produced by a vacuum pump and with the aid of a microwave generator at low temperature, and these solvents are recuperated in liquid form by condensation. During this regeneration phase, the parallel second device operates in the cleaning phase until the humidity sensor responds to lowered humidity. Both towers of the first device are then switched again into their starting phase and the above described process repeats itself.
A drawback of this process and of this installation is that, for uninterrupted operation, an apparatus is required which has at least two pairs each with two series connected adsorption towers, that is a total of four adsorption towers, in order to be able to continuously process the waste air and perform simultaneously an adsorption phase and a desorption phase.